1. Field of the Invention
The present invention relates to an illumination optical apparatus for illuminating an object to be illuminated in an arcuate or rectangular shape. More particularly, the invention relates to an illumination optical apparatus suitable for applications in exposure apparatus for fabrication of semiconductors and to a scanning exposure apparatus using it.
2. Related Background Art
An example of conventional illumination optical apparatus of such type is what is disclosed in U.S. Pat. No. 4,497,015 issued to Konno et al. The apparatus as disclosed has a plurality of optical integrators arranged between a point source of light and an object to be illuminated, by which a uniform intensity distribution can be obtained on the exit plane of the last optical integrator.
On the other hand, there is a scanning exposure method recently proposed, in which a rectangular or arcuate beam is formed to illuminate a reticle and in which the reticle and a wafer disposed conjugate with each other with respect to a projection optical system are moved in a certain direction, whereby a circuit pattern on the reticle is duplicated on the wafer with high throughput.
Since this scanning exposure method requires uniform illumination in a rectangular or arcuate area, an illumination optical apparatus which can obtain uniform illumination is such an area is required.